High-aspect-ratio WO3 nanoneedles modified with nickel-borate for efficient photoelectrochemical water oxidation

•WO3 nanoneedles were grown on FTO substrates for solar water oxidation.•Nickel-borate (Ni-Bi) was used as oxygen-evolving catalyst to modify WO3 nanoneedles.•Deposition of Ni-Bi on WO3 nanoneedles improves the activity toward O2 evolution reaction.•WO3 nanoneedles/Ni-Bi composites show superior photostability to WO3 nanoneedles.

Oxygen evolution reaction (OER) is the key process for solar powered water-splitting. In this work, we report the fabrication of the WO3 nanoneedles/nickel-borate composite photoanodes for efficient photoelectrochemical OER, with the high-aspect-ratio nanoneedles as light-absorbing material and the nickel-borate (Ni-Bi) as oxygen-evolving catalyst. We demonstrate that the combination of Ni-Bi with WO3 nanoneedles significantly enhances the activity of the photoanode toward OER by negatively shifting the onset potential of the photocurrent and improving the photocurrent within the entire oxygen-evolving potential region. Moreover, the WO3 nanoneedles/Ni-Bi composite photoanodes exhibit superior stability to the WO3 nanoneedles photoanodes in borate buffer solution at all oxygen-evolving potentials. The present result offers promising opportunities for using Ni-Bi as an oxygen-evolving catalyst to modify semiconductor photoanode to improve solar-to-oxygen efficiency.

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